Automatic Volume Limiter (AVL), or sometimes Automatic Volume Limiter System (AVLS) is an option, enabled through software or hardware, in music players such as, Cassette players, MP3 players and CD players, or other devices used with headphones such as the Sony PSP that limits the maximum volume level. The aim of this is to stop the headphones drowning out all other noise, and to limit the noise from the headphones being heard by other people.